The present invention relates to a method of wrapping elongated articles in groups.
More specifically, the present invention relates to a method of wrapping orderly groups of cigarettes, to which the following description refers purely by way of example.
Methods of wrapping orderly groups of cigarettesxe2x80x94hereinafter referred to simply as xe2x80x9cgroupsxe2x80x9dxe2x80x94normally comprise folding a sheet of wrapping material about a group to form a tubular wrapping; and closing two tubular portions, projecting from opposite ends of the group, onto the group itself. Formation of the tubular wrapping comprises a first folding step wherein the sheet of wrapping material is folded into a U; a second folding step wherein a first free flap of the sheet of wrapping material is folded into an L; and a third folding step wherein a second free flap of the sheet of wrapping material is folded into an L onto a third flap folded onto the group when making the U-shaped fold.
In known methods of a first type, the group is inserted inside a metal spindle, and a sheet of wrapping material is folded about the spindle. Methods of this type provide for forming sharp-edged foldsxe2x80x94particularly appreciated in the cigarette manufacturing industryxe2x80x94but involve extracting the spindle from the tubular wrapping, thus slowing down the wrapping unit as a whole.
In known methods of a second type, the sheet of wrapping material is folded directly about the group, so that the tubular wrapping has rounded edges with a radius of curvature substantially equal to the diameter of the cigarettes.
Given the current emphasis, in automatic machine design, on producing continuously-operating machines to increase output, wrapping methods of the first type are more or less discarded, by extraction of the group and wrapping from the spindle not being adaptable to continuously-operating machines.
One known method of wrapping groups on a continuously-operating machine normally comprises feeding a first and a second pocket continuously along a first and, respectively, second path having a common portion, along which the first pocket penetrates the second pocket to transfer an orderly group of cigarettes from the first to the second pocket together with a sheet of wrapping material, which is folded into a U, when transferring the group, and is then folded about the group by folding devices located along the second path. The first pocket comprises a first bottom wall and two lateral walls, and the second pocket comprises a second bottom wall and second lateral walls. When making the U-shaped fold, a portion of the sheet of wrapping material is gripped between the group and the second bottom wall; and two opposite, parallel flaps of the sheet of wrapping material are gripped between the first and second lateral walls. The first and second pocket are then fed separately along the respective paths, and the first pocket, obviously, is extracted from the second. When extracting the first lateral walls, the sheet of wrapping material may slip with respect to the second pocket and to the group housed inside the second pocket, even to the extent of impairing subsequent folds and formation of the wrapping as a whole. On the other hand, it is extremely difficult to determine the conditions resulting in such a difference in friction between the two first lateral walls and the flaps as to cause slippage of the sheet of wrapping material.
It is an object of the present invention to provide a method of wrapping elongated articles in groups, which may be implemented easily on an automatic, continuously-operating machine of the type described above, and which at the same time provides for preventing slippage of the sheet of wrapping material during the folding operations.
According to the present invention, there is provided a method of wrapping elongated articles in groups, the method comprising feeding a first and a second pocket continuously along a first and, respectively, second path having a common portion, along which the first pocket penetrates the second pocket to transfer a group from the first to the second pocket together with a sheet of wrapping material, the first and the second pocket comprising, respectively, a first and a second bottom wall, and first and second lateral walls; gripping a first and a second flap, opposite and parallel to each other, of the sheet of wrapping material between the first and second lateral walls; and extracting the first lateral walls from the second pocket; the method being characterized by compressing the group and a portion of the sheet of wrapping material between the first and second bottom wall when extracting the first lateral walls from the second pocket.
In other words, the sheet of wrapping material is compressed to prevent slippage of the sheet caused by extraction of the first lateral walls from the second pocket.